The leaders of the eurozone's biggest economies announced on Friday night that 1% of the European Union's GDP was to be set aside to help the continent grow its way out of the financial crisis. But doubts were immediately expressed as to what share of the package – said to be worth €130bn (£105bn) – would be genuinely new money.

After several hours of apparently tense discussions, there was no immediate agreement on a plan outlined by Italy's prime minister, Mario Monti, on Thursday, aimed at stabilising Europe's banks and protecting countries under attack in the markets.

"There was an agreement between all of us to use any necessary mechanism to obtain financial stability in the eurozone," said Mariano Rajoy, the Spanish prime minister, afterwards.

But the German chancellor, Angela Merkel, insisted that the EU must take full advantage of the instruments already at its disposal. Her remark suggested she is wary of two new funds – to guarantee bank depositors and as a lender of last resort to ailing banks – understood to have been on the agenda at Friday's talks.

In a sign that tempers are becoming increasingly frayed before next week's crucial summit, the normally gentlemanly Monti used his closing remarks to attack France and Germany publicly.

With Merkel and the French president, François Hollande, standing just feet from him on the podium, he reminded the world's media that it was not Greece or any of the other alleged EU basket cases that had first broken the rules on fiscal discipline in the eurozone, but the single currency's two biggest nations – albeit with the endorsement of Italy, which then held the EU presidency.

Friday's meeting of the big four leaders in Rome came as yet more gloomy eurozone economic indicators were released. German business confidence has fallen to a two-year low, while Italian consumer confidence has plunged to its lowest level on record. Monti's popular support is in decline as the Italian economy fights both recession and rising unemployment and Rome faces increased borrowing costs.

Hollande revealed that all four leaders were in favour of a European financial transactions tax, a small tax on all financial deals which was originally proposed to tame speculation in the financial markets. His comment followed agreement by a group of countries – not including the UK – at the EU finance ministers' meeting in Luxembourg to press ahead with plans for the tax.

David Hillman of the UK's Robin Hood Tax campaign – which backs the financial transactions tax and wants any cash raised to be earmarked for development – welcomed the agreement, but added that "the UK public will be rightly angry that George Osborne is resisting efforts to make the City pay its fair share".

He said that a Robin Hood tax would "boost growth as well as raising billions to tackle poverty and protect public services at home and abroad".

One of the keys to next week's summit will be the precise terms of the growth package. The €130bn would appear to represent a sum that might be raised or redirected from existing funds, rather than any commitment of new money. Nicholas Spiro, of Spiro Sovereign Strategy, said: "The pact has a shuffling of the deckchairs feel to it."

EU governments have already agreed to boost the capital of the European Investment Bank by €10bn, hoping it will be leveraged into €60bn in the financial markets for investment purposes. The growth package also appears to entail deploying up to €55bn in unspent EU structural funds.

Governments have already agreed to allow the sale of "project bonds" in the markets in the hope of raising capital for major infrastructure projects.

Another measure by which the summit will be judged is progress towards a project for guaranteeing financial stability which, according to an informed source, was being worked on by the "gang of four", including representatives of the European Central Bank (ECB), Eurogroup, and European commission and council. One aspect of the project was spelled out by Monti in an interview with the Guardian and other leading European newspapers on Thursday.

This would involve tying the purchase of sovereign bonds to the performance of the country in need of help. Virtuous states that had introduced structural reforms and contained their budget deficits would be rewarded.

In its present form, the plan would see the buying done by the European Financial Stability Facility, the bailout fund for states, rather than the European Central Bank.

The other aspects of the plan would involve the creation of two new rapid response funds: one would guarantee bank depositors; the other could be used to deal with institutions such as Spain's Bankia that looked as if they might pose a threat to the entire eurozone, creating, if not a bank of last resort, a fund of last resort.

Merkel appeared to be less than convinced of this idea, or at least bent on ensuring it was accompanied by iron controls. In an apparent reference to the still-secret plan, she said that if Germany were to give money to a Spanish bank she would have no way of knowing how it was spent – and that would be a "giant problem" for her.

The proposed new bank intervention fund appears to require new administration because the ECB, with a mandate to deal strictly with monetary policy, could not run the proposed new funds.

• This article was amended on 26 June 2012 because the original converted €130bn to £105m. This has been corrected.